CMP (chemical mechanical polishing) is employed for polishing surfaces of wafers required to be highly flat, such as semiconductor wafers. CMP is a technique in which a polishing agent having an etching effect on the work is used to etch the work while mechanically polishing the work with abrasive grains contained in the polishing agent.
Conventionally, single side polishing apparatuses such as a single side polishing apparatus 500 shown in FIG. 8 have been used for CMP. The single side polishing apparatus 500 of FIG. 8 is only an example of wafer single side polishing apparatuses, and includes a head 502 for retaining a wafer and a surface plate 510 having a polishing cloth 512. In the single side polishing apparatus 500, the head 502 retains a wafer and meanwhile presses a polishing target surface of the wafer against the polishing cloth 512 provided on the top surface of the rotating surface plate 510. The head 502 and the surface plate 510 are relatively moved by rotating the head 502 and the surface plate 510 together, thereby polishing the polishing target surface of the wafer while supplying a polishing agent 528 from a polishing agent supply means 526.
As an example of such a single side polishing apparatus, JP 2000-077369 A (PTL 1) discloses a single side polishing apparatus which measures the thicknesses of a center portion and a peripheral portion of a wafer, and controls the rotation speed of a head and a surface plate based on the measurement result, thereby leveling the amount of polishing on the wafer surface.